This invention relates to mechanical seals of the type used for sealing between a housing, such as a pump housing, and a rotating shaft, such as the pump impeller shaft, such seals employing relatively rotating sealing elements which have contacting radial annular faces lapped to extremely flat finishes in order to provide a fluid seal at the interface of the sealing surfaces. One of the sealing elements or sealing rings is nonrotating and is mounted in the housing; the complementary ring is mounted on the shaft or a shaft sleeve for rotation therewith. One of the rings is biased, as by a spring or springs, for axial movement toward the other sealing ring for contact of the complementary faces to form the annular sealing interface. One of the peripheries of the interface being in contact with fluid under pressure in the pump housing and the other periphery being at a lower or atmospheric pressure, there is thus a pressure gradient therebetween, so that a small amount in the form of a very thin film of the fluid may flow across the interface, tending to cool and lubricate the faces, resulting in reduced heat buildup and wear of the sealing surfaces. The thin film flow across the interface may be inadequate to cool and lubricate the surfaces when pumping high temperature fluids, particularly at very high speeds. Alleviation of this problem has been accomplished in the past by pumping a cooling liquid from an auxiliary source through a conduit to a groove or grooves opening into the stationary sealing ring.